Method and system of uniform wireless power distribution within a chamber

ABSTRACT

A system is disclosed which includes a chamber, one or more transmitters configured to emit EM radiation, one or more power harvesters, one or more EM stirrer, and a processing system configured to a) receive a measure of dimensional characteristics of the chamber b) control the one or more EM stirrers, c) evaluate statistical properties of the statistical EM environment, d) set a new criterion for acceptable statistical properties of the statistical EM environment, e) measure a lowest usable frequency of the chamber below which the statistical properties are not acceptable according to a predetermined criterion, f) determine an efficiency profile of the one or more power harvesters versus frequency, g) select an operating frequency that maximizes efficiencies of the one or more power harvesters, h) measure a collective efficiency of the chamber, and i) return to step d if the measured collective efficiency is below a predetermined efficiency threshold.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application is a continuation of U.S. Non-Provisionalpatent application Ser. No. 16/843,749 filed on 8 Apr. 2020 which isrelated and claims the priority benefit to U.S. Provisional PatentApplication Ser. No. 62/831,125 filed Apr. 8, 2019; and is related toU.S. Provisional Patent Application Ser. No. 62/831,159 filed Apr. 8,2019, and to U.S. Provisional Patent Application Ser. No. 62/851,129filed May 22, 2019, the contents of each of which are herebyincorporated by reference in its entirety into the present disclosure.

STATEMENT REGARDING GOVERNMENT FUNDING

This invention was not made with government funding.

TECHNICAL FIELD

The present disclosure generally relates to wireless power transmission,and in particular, to uniform wireless power transmission within achamber.

BACKGROUND

This section introduces aspects that may help facilitate a betterunderstanding of the disclosure. Accordingly, these statements are to beread in this light and are not to be understood as admissions about whatis or is not prior art.

Uniform wireless power transmission within a chamber is of highimportance in many applications. One such application is liophilizationwhich is generally known as freeze drying. This process is widely usedin both the pharmaceutical and food industries. This process involvescontrollably removing water content from a frozen solution.Liophilization allows drugs or food products to be kept in a stable formfor easier and longer storage. When the drug is required to be used, itcan be easily rehydrated by adding water. Anti-cancer and anti-allergicdrugs, attenuated vaccines, antibiotics, and probiotics are examples ofsuch drugs that utilize lyophilization.

The typical operation of lyophilization includes loading lyophilizate(the drug solution being lyophilized) into vials. These vials aresubsequently loaded into a freeze-drying chamber where they undergo thelyophilization.

The process of freeze drying can be divided into three main steps:freezing, primary drying and secondary drying, while constantly keepingthe maximum product temperature below a critical temperature to avoidruining the product. Therefore, continuous monitoring of thelyophilizate's temperature during the process is necessary for asuccessful and efficient lyophilization.

While monitoring of individual vials is important, techniques in thecurrent state of the art only allow monitoring the chamber ambienttemperature. One of the challenges for developing wireless sensors tomonitor the vials' temperatures within the chamber is the need forwireless power transfer system to power these sensors in anelectromagnetically difficult environment.

As a result, there is an unmet need for a wireless power transmission(WPT) system and method that can transfer power to sensors with auniform distribution at a large number of positions within a chamber.

SUMMARY

A method of uniform wireless power distribution within a chamber isdisclosed. The method includes measuring dimensional characteristics ofa chamber, having a transmitter and a plurality of power harvesters. Themethod further includes creating a statistical electromagneticenvironment by stirring electromagnetic waves generated by anelectromagnetic source inside the chamber. In addition, the methodincludes evaluating statistical properties of the statisticalelectromagnetic environment, and setting a new criterion for acceptablestatistical properties of the statistical electromagnetic environment.The method also includes measuring a lowest usable frequency of thechamber below which the statistical properties of the statisticalelectromagnetic environment are not acceptable according to apredetermined criterion, and determining an efficiency profile of theplurality of power harvesters versus frequency at frequencies higherthan the lowest usable frequency. Additionally, the method includesselecting an operating frequency that maximizes efficiencies of theplurality of power harvesters, and measuring a collective efficiency ofthe chamber. In case the measured collective efficiency is below apredetermined efficiency threshold, the method includes returning tosetting a new criterion.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flowchart describing steps of a method of uniform wirelesspower distribution within a chamber, according to the presentdisclosure.

FIG. 2A is an exemplary schematic of the chamber including a motorassembly in which the method of FIG. 1 is performed.

FIG. 2B is an exemplary schematic of the motor assembly of FIG. 2A.

FIG. 3 is an example graph of acceptance ratio (which is a measure offit quality of the statistical function) vs. frequency in GHz, showing alowest usable frequency (LUF) according to a predetermined threshold.

FIG. 4 is a graph of threshold for a measure of losses (Qthr) and actuallosses (Qc) vs. frequency.

FIG. 5 is an example graph comparing actual power measurements expressedas P_(Ravage-to-min) to average to minimum power ration expressed as ATMPR_(thr) vs. frequency.

FIG. 6 is an example of a computer system that can interface with theuniform wireless power distribution system of the present disclosure.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of thepresent disclosure, reference will now be made to the embodimentsillustrated in the drawings, and specific language will be used todescribe the same. It will nevertheless be understood that no limitationof the scope of this disclosure is thereby intended.

In the present disclosure, the term “about” can allow for a degree ofvariability in a value or range, for example, within 10%, within 5%, orwithin 1% of a stated value or of a stated limit of a range.

In the present disclosure, the term “substantially” can allow for adegree of variability in a value or range, for example, within 90%,within 95%, or within 99% of a stated value or of a stated limit of arange.

A novel wireless power transmission (WPT) system and method that cantransfer power to sensors with a uniform distribution in the spacewithin a chamber is disclosed. The method includes utilizing statisticalelectromagnetism methodology in determining a frequency from analternating power source that can generate the desired uniform powerdistribution at these positions.

Referring to FIG. 1, a flowchart describing the steps of a method 10according to the present disclosure is shown. The method begins bymeasuring the dimensional characteristics of a chamber in which uniformpower distribution is desired, as shown by block 12. An example of suchchamber is shown in FIG. 2A, as identified by reference numeral 102.This step includes determining volume, surface area, largest dimension,and smallest dimension of the chamber. As shown in FIG. 2A, the chambercontains a transmitting antenna 106 that is coupled to anelectromagnetic power source, a number of receiving antennas 108, eachone is the first stage of a wireless power harvester device 109, that isintended to harvest the uniformly distributed power inside the chamber102, and a mechanical stirrer 104 of which the functionality will bemade clear, below. The next step is to create a statistical (random)electromagnetic environment, as provided by block 16 in FIG. 1. In thepresented example, this is achieved by continuously rotating themechanical stirrer 104 inside the chamber which continuously changes theboundary conditions for the electromagnetic waves resonating inside thechamber 102. This in turn results in a continuously changingelectromagnetic fields structures inside the chamber which promotes arandom electromagnetic environment. The next step is to evaluate thestatistical properties of the created statistical (random)electromagnetic environment versus frequency as provided by the block18. The objective in this step is to measure from this evaluation howclose is the created environment to an ideal random performance underwhich the properties of the theory of statistical electromagneticsapply. One of these properties that is essential to the presentedapplication is the independence of the received power within the chamberon the position, in other words the uniformity of the received power.Since it is quite difficult, if not impossible, to create an ideallyrandom electromagnetic environment, the next step is setting thresholdsfor the statistical properties that results in a specified (by aspecified standard deviation from the mean) field uniformity, asindicated by block 20 of FIG. 1. The next step is to determine thelowest usable frequency which is the minimum frequency below which thestatistical properties are below the set thresholds, as indicated byblock 22. The next step is to select the type(s) of the wireless powerharvesters depending on the application, as indicated by block 24. It isknown that the efficiency of the power harvester depends on the amountof input wireless power available at the location of the harvester. Itis also known that this efficiency peaks at some input wireless powerand decays if this power increases or decreases. Therefore, it ispreferable to utilize identical power harvesters or different powerharvesters with similar efficiency profiles. Consequently, maintaining auniform power distribution at all harvesters' locations results inachieving the maximum collective efficiency from these harvesters. Thenext step is to measure the achieved uniformity in power distributionversus frequency in terms of the associated standard deviation, as shownin block 26. The next step is to check whether the uniformity isacceptable, as provided in block 28. If not, the criteria for acceptablestatistical properties should be updated such that a more ideal randomenvironment is obtained and, hence, a more uniform power distribution isachieved by returning to block 20. If yes, the method 10 proceeds to thenext step which is to measure the efficiency profile of the harvestersversus frequency for all frequencies that is higher than the minimumfrequency at which the uniformity evaluated in the previous step isacceptable, as provided by block 30. The next step is to select thefrequency at which the efficiency profiles is maximum, as provide byblock 32. The next step is to measure the collective efficiency of thewireless power transmission system which is the ratio between the totalharvested power from all harvesters and the input power at thetransmitting antenna, as provided by block 34. Finally, if bettercollective efficiency is required, the criteria for acceptablestatistical properties should be updated accordingly and the entireprocedure afterwards is repeated by returning to block 20. Ifacceptable, then the method 10 is completed.

Referring to FIG. 2A, a novel electromagnetic system 100 according tothe present disclosure is shown. In FIG. 2A, the system 100 includes achamber 102 which according to an embodiment is a metallic Faradaychamber, however, other electromagnetically limiting chambers are withinthe scope of the present disclosure. Within the chamber 102 there existsa motor assembly 104, and an alternating frequency power transmitter106. The motor assembly 104 is shown in FIG. 2B, as part of a subsystem150. The motor assembly 104 includes a motor 156, a stirrer 158 drivenby a shaft 160. While the motor assembly 104 is shown inside the chamber102, the motor 156 can be placed outside of the chamber 102 with thestirrer 158 placed inside the chamber 102. The stirrer 158 is shown asbeing positioned in one corner of the chamber 102, however, otherpositions are also within the scope of the present disclosure. Only onestirrer 158 is used in this embodiment, however, multiple stirrersand/or motors are within the scope of the present disclosure. As shownin FIG. 2B, the motor assembly 104 is coupled to an encoder 154, whichcoupled to a processor 152. Continuous rotating of the stirrer,according to one embodiment, continuously changes the electric andmagnetic fields structures to thereby vary statistical electromagneticenvironment inside the chamber, in order to simulate a rich multipathelectromagnetic environment.

According to another embodiment, the electric and magnetic fields withinthe chamber are continuously changed by electronic stirring, in whichthe frequency of the alternating transmitted power is continuouslychanged. For example, the frequency is continuously changed apredetermined bandwidth about a selected frequency f₀, as discussedfurther below. Alternatively, the electric and magnetic fields arecontinuously changed by continuously changing amplitude of the appliedalternating wireless power by a predetermined amplitude.

Next, with reference back to FIG. 1, one or more positions within thechamber are identified in order to determine the proper frequency rangeof transmission, as shown in block 18. These locations correspond tolocations of temperature sensors to be powered by the wireless powertransmission. Next, a matrix is generated based on the positions 180_(i) (see FIG. 2A) and the frequency of the alternating transmittedpower as it is varied by selection from the plurality of predeterminedplurality of frequencies, as shown in block 20. For example, suppose 10positions have been selected, the number of electromagnetic structuresis 360 corresponding to the mechanical paddle having 360 discreterotational positions, and each electromagnetic structure is recorded at1000 frequencies, the matrix will have 3600 rows and 1000 columns,correspondingly. Next the matrix is applied to a statistical function,as shown in block 22. In one example, the statistical function can be anexponential function. For example, the exponential function can beexpressed as:

f _(x) ₂ ₂ (x)=(½σ²)exp(−x/σ2)U(x)

, wherein f_(x) ₂ ₂ is a Chi-Squared distribution function with twodegrees of freedom, σ is the standard deviation of the parent normaldistribution (any Chi-squared distribution is composed of the sum ofsquared ‘n’ normal distributions, where ‘n’ is the degree of freedom ofthe resulting Chi-Squared distribution—these normal distributions arereferred to as parent normal distribution), andx is the received power.

Upon application of the above-described matrix to the statisticalfunction, a graph is thus generated describing acceptance ratiopercentage (which is a measure of fit quality of the statisticalfunction) vs. frequency. An example of this graph is shown in FIG. 3.Next in method of FIG. 1, is the step of determining where the graphcrosses a predetermined threshold for acceptance ration % (in the graphof FIG. 3, this threshold was equated to 5%), as provided in block 24; alowest usable frequency (LUF) is thus identified. In FIG. 3, the LUF isabout 6 GHz.

Generally, higher frequencies yield better statistical properties. Atthe LUF, there is enough electromagnetic modes (i.e., simultaneouslycoexisting electromagnetic structures) in the chamber to generate astatistical electromagnetic environment. However, using the LUF is notnecessarily sufficient for creating an acceptable statisticalelectromagnetic environment. A range of frequencies, f₀, greater thanLUF valid for this purpose should be determined, as provided in block26. An example of these tests is the chamber quality factor test and theaverage to minimum received power test.

Next, a threshold for a measure of losses (Q_(thr)) around LUF isdetermined, as provided in block 28. The Q_(thr) is calculated based on:

${Q_{thr} = {\left( \frac{4\pi}{3} \right)^{\frac{2}{3}}\frac{3V^{\frac{1}{3}}}{2\lambda}}},$

wherein V is the volume of the chamber, and λ is wavelength of thealternating power, where λ is calculated based on:

-   -   λ=c₀/f₀, where    -   c₀ is the speed of light.

Next, actual losses (Q_(c)) of the chamber is measured at frequency f₀(the initial value for f₀ is the LUF), as shown in block 30 on thesecond page of FIG. 1. The losses are the result of i) Joules-heat owingto imperfect conductive walls generating currents that turn into heat,or ii) dielectric losses which also turn into losses generating heat.The losses in the chamber Q_(c) is determined according to oneembodiment by i) measuring a power delay profile (PDP) at a frequencyf₀; ii) plotting the PDP on a dB scale; iii) fitting the PDP curve to alinear function; iv) determining slope of the linear function forming atime constant (τ_(l)) of the chamber at the frequency f₀; v) calculatingQ_(c) as 2πf₀τ_(l); and vi) repeating steps (i) through (v) fordifferent frequencies f₀. A graph of Q_(thr) and Q_(c) is shown in FIG.4. At 6 GHz the measured Q_(c) is about 40 dB. Next Q_(thr) and Q_(c)are compared, as provided in block 32. If Q_(c)>>Q_(thr), as provided inthe decision block 32, then the method proceeds to the next step asshown in block 38, otherwise, the method increments f₀, as provided inblock 36, and returns to step BB, i.e., block 26, (where the newincremented frequency f₀ is chosen as compared to the previous value off₀).

If the Q_(c)>>Q_(thr) then the method proceeds to measuring the averageand minimum power at the plurality of positions for frequencies greaterthan or equal to LUF, as provided in the block 38. Once the average andminimum power are measured, then a method of the present disclosureproceeds to calculating the ratio of the average received power to theminimum received power (P_(Ravage-to-min)), as shown in block 40. Nextthe method 10 compares the calculated P_(Ravage-to-min) to apredetermined average to minimum power ratio (ATMPR_(thr)), as providedin block 42, where ATMPR_(thr) is calculated based on:

ATMPR_(thr)[dB]=10 log₁₀(N)+2.5, where

N is the number of stirring points used while collecting data-sets. Inthis embodiment, N refers to the number of paddle steps (e.g., 360 as inthe example provided above with respect to the number of positions ofthe mechanical paddle). An example of a graph comparing actual powermeasurements expressed as P_(Ravage-to-min) to ATMPR_(thr) is shown inFIG. 5. The measured ATMPR swings about the predetermined ATMPR_(thr)discussed above. Smaller swing about this value implies betterstatistical properties. If, at the last selected value of f₀, the swingrange is small, based on a decision block 44, then this value of f₀ isaccepted as the WPT frequency. Otherwise, the method according to thepresent disclosure returns to choosing a new f₀ and thereby repeatingthe steps forward of choosing a new f₀, as shown in the decision block44.

A system comprising more than a general purpose computer can be used toassemble the data for the above-described steps. According to oneembodiment, this system may contain accessories including i) a samplingprobe to measure the field anywhere within the chamber; ii) an amplifierto control the input power; iii) a signal generator to generate thedesired frequency and to vary the driving frequency (in case electronicstirring by changing frequency is employed); iv) a noise generator tochange the driving signal amplitude (in case electronic stirring bychanging amplitude is employed); v) a paddle with rotation mechanism (incase mechanical stirring is employed); and a code implementation for thepostprocessing of the data-sets.

Referring to FIG. 6, an example of a computer system is provided thatcan interface with the above-discussed uniform wireless powerdistribution system. Referring to FIG. 6, a high-level diagram showingthe components of an exemplary data-processing system 1000 for analyzingdata and performing other analyses described herein, and relatedcomponents. The system includes a processor 1086, a peripheral system1020, a user interface system 1030, and a data storage system 1040. Theperipheral system 1020, the user interface system 1030 and the datastorage system 1040 are communicatively connected to the processor 1086.Processor 1086 can be communicatively connected to network 1050 (shownin phantom), e.g., the Internet or a leased line, as discussed below.The imaging described in the present disclosure may be obtained usingimaging sensors 1021 and/or displayed using display units (included inuser interface system 1030) which can each include one or more ofsystems 1086, 1020, 1030, 1040, and can each connect to one or morenetwork(s) 1050. Processor 1086, and other processing devices describedherein, can each include one or more microprocessors, microcontrollers,field-programmable gate arrays (FPGAs), application-specific integratedcircuits (ASICs), programmable logic devices (PLDs), programmable logicarrays (PLAs), programmable array logic devices (PALs), or digitalsignal processors (DSPs).

Processor 1086 can implement processes of various aspects describedherein. Processor 1086 can be or include one or more device(s) forautomatically operating on data, e.g., a central processing unit (CPU),microcontroller (MCU), desktop computer, laptop computer, mainframecomputer, personal digital assistant, digital camera, cellular phone,smartphone, or any other device for processing data, managing data, orhandling data, whether implemented with electrical, magnetic, optical,biological components, or otherwise. Processor 1086 can includeHarvard-architecture components, modified-Harvard-architecturecomponents, or Von-Neumann-architecture components.

The phrase “communicatively connected” includes any type of connection,wired or wireless, for communicating data between devices or processors.These devices or processors can be located in physical proximity or not.For example, subsystems such as peripheral system 1020, user interfacesystem 1030, and data storage system 1040 are shown separately from thedata processing system 1086 but can be stored completely or partiallywithin the data processing system 1086.

The peripheral system 1020 can include one or more devices configured toprovide digital content records to the processor 1086. For example, theperipheral system 1020 can include digital still cameras, digital videocameras, cellular phones, or other data processors. The processor 1086,upon receipt of digital content records from a device in the peripheralsystem 1020, can store such digital content records in the data storagesystem 1040.

The user interface system 1030 can include a mouse, a keyboard, anothercomputer (connected, e.g., via a network or a null-modem cable), or anydevice or combination of devices from which data is input to theprocessor 1086. The user interface system 1030 also can include adisplay device, a processor-accessible memory, or any device orcombination of devices to which data is output by the processor 1086.The user interface system 1030 and the data storage system 1040 canshare a processor-accessible memory.

In various aspects, processor 1086 includes or is connected tocommunication interface 1015 that is coupled via network link 1016(shown in phantom) to network 1050. For example, communication interface1015 can include an integrated services digital network (ISDN) terminaladapter or a modem to communicate data via a telephone line; a networkinterface to communicate data via a local-area network (LAN), e.g., anEthernet LAN, or wide-area network (WAN); or a radio to communicate datavia a wireless link, e.g., WiFi or GSM. Communication interface 1015sends and receives electrical, electromagnetic or optical signals thatcarry digital or analog data streams representing various types ofinformation across network link 1016 to network 1050. Network link 1016can be connected to network 1050 via a switch, gateway, hub, router, orother networking device.

Processor 1086 can send messages and receive data, including programcode, through network 1050, network link 1016 and communicationinterface 1015. For example, a server can store requested code for anapplication program (e.g., a JAVA applet) on a tangible non-volatilecomputer-readable storage medium to which it is connected. The servercan retrieve the code from the medium and transmit it through network1050 to communication interface 1015. The received code can be executedby processor 1086 as it is received, or stored in data storage system1040 for later execution.

Data storage system 1040 can include or be communicatively connectedwith one or more processor-accessible memories configured to storeinformation. The memories can be, e.g., within a chassis or as parts ofa distributed system. The phrase “processor-accessible memory” isintended to include any data storage device to or from which processor1086 can transfer data (using appropriate components of peripheralsystem 1020), whether volatile or nonvolatile; removable or fixed;electronic, magnetic, optical, chemical, mechanical, or otherwise.Exemplary processor-accessible memories include but are not limited to:registers, floppy disks, hard disks, tapes, bar codes, Compact Discs,DVDs, read-only memories (ROM), erasable programmable read-only memories(EPROM, EEPROM, or Flash), and random-access memories (RAMs). One of theprocessor-accessible memories in the data storage system 1040 can be atangible non-transitory computer-readable storage medium, i.e., anon-transitory device or article of manufacture that participates instoring instructions that can be provided to processor 1086 forexecution.

In an example, data storage system 1040 includes code memory 1041, e.g.,a RAM, and disk 1043, e.g., a tangible computer-readable rotationalstorage device such as a hard drive. Computer program instructions areread into code memory 1041 from disk 1043. Processor 1086 then executesone or more sequences of the computer program instructions loaded intocode memory 1041, as a result performing process steps described herein.In this way, processor 1086 carries out a computer implemented process.For example, steps of methods described herein, blocks of the flowchartillustrations or block diagrams herein, and combinations of those, canbe implemented by computer program instructions. Code memory 1041 canalso store data, or can store only code.

Various aspects described herein may be embodied as systems or methods.Accordingly, various aspects herein may take the form of an entirelyhardware aspect, an entirely software aspect (including firmware,resident software, micro-code, etc.), or an aspect combining softwareand hardware aspects. These aspects can all generally be referred toherein as a “service,” “circuit,” “circuitry,” “module,” or “system.”

Furthermore, various aspects herein may be embodied as computer programproducts including computer readable program code stored on a tangiblenon-transitory computer readable medium. Such a medium can bemanufactured as is conventional for such articles, e.g., by pressing aCD-ROM. The program code includes computer program instructions that canbe loaded into processor 1086 (and possibly also other processors), tocause functions, acts, or operational steps of various aspects herein tobe performed by the processor 1086 (or other processors). Computerprogram code for carrying out operations for various aspects describedherein may be written in any combination of one or more programminglanguage(s), and can be loaded from disk 1043 into code memory 1041 forexecution. The program code may execute, e.g., entirely on processor1086, partly on processor 1086 and partly on a remote computer connectedto network 1050, or entirely on the remote computer.

Those having ordinary skill in the art will recognize that numerousmodifications can be made to the specific implementations describedabove. The implementations should not be limited to the particularlimitations described. Other implementations may be possible.

1. A system for providing uniform wireless power distribution within achamber, comprising: a chamber; one or more transmitters about thechamber configured to emit electromagnetic (EM) radiation; one or morepower harvesters disposed within the chamber; one or more EM stirrerdisposed within the chamber and configured to stir EM waves to therebygenerate a statistical EM environment within the chamber; and aprocessing system having a processor and software maintained on anintangible memory configured to: a. receive a measure of dimensionalcharacteristics of the chamber, b. control the one or more EM stirrersto thereby create a statistical EM environment by stirring EM wavesgenerated within the chamber, c. evaluate statistical properties of thestatistical EM environment, d. set a new criterion for acceptablestatistical properties of the statistical EM environment, e. measure alowest usable frequency of the chamber below which the statisticalproperties of the statistical EM environment are not acceptableaccording to a predetermined criterion, f. determine an efficiencyprofile of the one or more power harvesters versus frequency atfrequencies higher than the lowest usable frequency, g. select anoperating frequency that maximizes efficiencies of the one or more powerharvesters; h. measure a collective efficiency of the chamber; i. returnto step d if the measured collective efficiency is below a predeterminedefficiency threshold.
 2. The system of claim 1, wherein the measurementof the dimensional characteristics of the chamber is based onmeasurement of volume, surface area, a largest dimension, and a smallestdimension of the chamber.
 3. The system of claim 1, wherein the creationof the statistical EM environment includes placement of the one or moretransmitters inside the chamber.
 4. The system of claim 1, wherein thecreation of the statistical EM environment includes placement of the oneor more transmitters outside the chamber.
 5. The system of claim 1,wherein the creation of the statistical EM environment includescontinuously changing the electric and magnetic fields within thechamber.
 6. The system of claim 5, wherein the continuously changing ofthe electric and magnetic fields within the chamber includes stirringthe electric and magnetic fields.
 7. The system of claim 6, wherein thestirring of the electric and magnetic fields includes mechanicalstirring.
 8. The system of claim 7, the mechanical stirring includes amechanical paddle continuously moving inside the chamber.
 9. The systemof claim 8, wherein the movement of the mechanical paddle includesrotating.
 10. The system of claim 6, wherein the EM stirring is achievedby electronic stirring.
 11. The system of claim 10, frequency of the oneor more transmitters is continuously changed.
 12. The system of claim 1,wherein the evaluation of statistical properties of the statistical EMenvironment includes estimation of the statistical properties by achamber quality factor.
 13. The system of claim 1, wherein theevaluation of statistical properties of the statistical EM environmentincludes estimation of a statistical test on one or more EM parameters.14. The system of claim 1, wherein the evaluation of statisticalproperties of the statistical EM environment includes estimation ofaverage to minimum power ratios obtained from a plurality of samples ofreceived powers at a plurality of locations and at a plurality of times.15. The system of claim 1, wherein the selection of an operatingfrequency that maximizes efficiencies of the plurality of powerharvesters is based on the processor i) select one or more identicalpower harvesters of the plurality of power harvesters; and ii) determinea frequency at which the efficiency is maximum for all the plurality ofpower harvesters based on the selected power harvesters.
 16. The systemof claim 1, wherein the collective efficiency includes the ratio oftotal harvested power from the one or more power harvesters to totalinput EM power injected inside the chamber
 17. The system of claim 16,wherein the selection of an operating frequency that maximizesefficiencies of the plurality of power harvesters is based on theprocessor i) select one or more different power harvesters of theplurality of power harvesters; and ii) determine a frequency at whichthe efficiency is maximum for all the plurality of power harvestersbased on the selected power harvesters.